Characterization of Soil Amended with the By-Product of Corn Stover Fermentation

Corn stover harvested for ethanol production reduces the amount of residue returned to the soil. Crop residues Corn (Zea mays L.) stover is a potential biofuel; however, removing on the soil surface are important in controlling wind this stover from the land may increase the risk of erosion and reduce soil organic matter (SOM). Land application of corn stover fermentaand water erosion (Lindstrom, 1986). Removal of corn tion by-product, which is about 70% lignin, may reduce the environresidue on both reduced tillage and no-till systems inmental risk from biofuel harvest by helping to stabilize soil structure. creased water runoff and soil erosion in the NorthwestA column study, with soil collected from a toeslope (noneroded, ern Corn Belt of USA (Lindstrom, 1986). The amount Svea; fine loamy, mixed, superactive, frigid Pachic Hapludoll) and a of residue that can be removed without increasing the shoulder slope (severely eroded, Langhei; fine loamy, mixed, superacerosion risk is dependent on a soil’s potential erodibility tive, frigid Typic Eutrudepts) was conducted to evaluate the effect (Lindstrom and Holt, 1983). Lindstrom and Holt (1983) of fermentation by-product on soil properties. Soil was either not found that about 59% of residue was available for reamended (control) or amended with corn stover or by-product at moval in all major land use areas, when the only crite0.75, 3.0, and 6.1 g kg 1. Soils were incubated for 123 d at ambient rion for removal was soil erosion. It should be noted temperature in a laboratory, with an initial water-filled pore space (WFPS) of 0.6 m3 m 3 and drying cycles to 0.35 m3 m 3 WFPS. Comthat the amount removed varied from 0 to 100% depared with the control, amending soil with 6.1 g by-product kg 1 pending on erosion risk (Lindstrom and Holt, 1983; increased CO2 flux by 68% and increased soluble C and microbial Nelson, 2002). Recent reviews suggest that 20 (Nelson, biomass C by about 20%. In the severely eroded soil, humic acid 2002) to 30% (McAloon et al., 2000) of the total stover concentration (r2 0.97, p 0.009) and aggregate stability (r2 0.98, production could be made available for biofuel, based p 0.005) increased linearly with increased by-product concentration. on ground cover requirements to control erosion. Water-holding capacity, bulk density, and aggregate distribution were Guidelines on how much residue can be removed not changed by soil amendments. Careful management of stover refrom a given field still need to be resolved. In addition, moval (avoiding eroded or erosion prone areas) and selective placedata are still needed to determine whether managing for ment and rates of the by-product will contribute to a sustainable use erosion is sufficient to maintain SOM levels (Wilhelm et of corn stover for ethanol production. al., 2003). Wilhelm et al. (2003) reported that contribution ratio of root (unharvestable material) to aboveground residue averaged 1.9, ranging from 0.8 to 2.6. B of fossil fuels is a major contributor to Roots provide an important contribution to soil organic atmospheric CO2 (IPCC, 1996). As an alternative, C (SOC), but aboveground residue also contributes to the United States Department of Energy and private forming SOC. Clapp et al. (2000) found a decline in the enterprise are developing a fermentation process for mass of SOC at the end of 13 yr, if C inputs were limited producing ethanol from high-cellulose biomass (Dito unharvestable C inputs for several tillage systems pardo, 2000; Hettenhaus et al., 2000). Corn stover and including no tillage. other plant materials with a high concentration of celluRemoval of corn stover also removes the valuable lose have potential as biofuel (e.g., ethanol production). plant nutrients contained in the stover. Once removed, Use of biofuel may partially offset energy requirements these nutrients are not cycled through the soil. Corn currently fulfilled by fossil fuels (Paustian et al., 1998). stover contains from 5.7 to 12.3 g N kg 1 (Burgess et A complete life-cycle analysis of this process includes al., 2002; Green et al., 1995; Lindstrom and Holt, 1983; comparing possible economical and environmentally Mubarak et al., 2002; Natural Renewable Energy Labosound uses for the by-product remaining after the ferratory [NREL], 2002), 1.8 to 2.9 g P kg 1, and 13.3 to mentation of corn stover, such as production of electric24.9 g K kg 1 (Lindstrom and Holt, 1983; Mubarak et ity or use as a soil amendment. al., 2002). The by-product remaining after fermentation of corn stover contains 600 to 700 g lignin kg 1 and 20 g J.M.F. Johnson, D. Reicosky, M. Lindstrom (retired), and W. VoorN kg 1 (NREL, 2002). In contrast, baled corn stover hees (retired), USDA-ARS, 803 Iowa Ave., Morris, MN 56267; B. Sharratt, USDA-ARS, 213 Smith Hall, WSU, Pullman, WA 99164contains about 200 g lignin kg 1 and 7 g N kg 1 (NREL, 6120; L. Carpenter-Boggs, Dep. of Plant Pathology, P.O. Box 646430, 2002). The by-product of stover fermentation if applied Washington State University, Pullman, WA 99164-6430. The use of to soil at the same rate would provide about three times trade, firm, or corporation names in this publication is for the informaas much lignin and N compared with stover. tion and convenience of the reader. Such use does not constitute an Soil organic matter is important for many soil funcofficial endorsement or approval by the USDA or the Agricultural Research Service of any product or service to the exclusion of others tions by providing energy, substrates, and biological dithat may be suitable. The USDA is an equal opportunity provider and versity (Franzluebbers, 2002). Adams (1973) and Hudemployer. Number 140108. Received 12 Oct. 2002. *Corresponding son (1994) found that a 2% decrease in SOM increased author ([email protected]). Abbreviations: SOC, soil organic carbon; SOM, soil organic matter; Published in Soil Sci. Soc. Am. J. 68:139–147 (2004).  Soil Science Society of America WFPS, water-filled pore space; NREL, National Renewable Energy Laboratory, Golden, CO. 677 S. Segoe Rd., Madison, WI 53711 USA